The Rusalka BugMistress is a Satan form of The Bugmaster (Bianca Beakley), She's a Mistress of Satan desiring to get the major attention of her lesbian girlfriend Aynaet Teal.

Her abilities are: Summoning Flood Water or Tsunami to drown the victim, and Breathe ice to inflict stabbing victims.

Bio:

A few months after Bianca Beakley is no longer the News Anchor, she gets fired. Her voice's manufacturing defect has left her sounding anything but replaceable with a devilish, horrible. She signed up the contact to join the Satan Queen's side from the Curse into becoming Satan Gang members in the depths of a Devil Swamp castle from Yoshi's Swamp Island, she is only companions are a band of Envy frogs (Frog Pirates). She knows someone will want her if only she can find a beautiful voice to recover herself and murder the hero miserably.

In the origin story diary, she did have a girlfriend (Cinnamon Teal) who began dating for both of them. Still, when she and her girlfriend signed the contract from Satan Queen, that she had a devil woman voice, she was disappearing and eventually found herself in a Yoshi's Swamp Island.

She first encounters Mario and Yoshi when she and Frog Pirate are going out for their evening stroll. When she hears that Mario was looking for his friends, she offers him a ride, initially offering to help Mario find her girlfriend before she murders him with an Envy effect. But even though he refuses to think it's a trap, she insists on it, and the Frog Pirates' mute ventriloquist dummies who serve as her enforcers put Mario and Yoshi into the carriage and throw them away from the swamp to find the Esuna Voice Pill.

It is then revealed that Rusalka BugMistress is, in fact, a defective scary lady duck who spent most of her existence having a malfunctioning delvish voice, after noticing Mario has one that works, which she wants. As the years passed, Rusalka had been sitting unused in the Yoshi's Swamp Island, desperate to work again so she can get dated by her girlfriend Cinnamon Teal, who is frequently given Yoshi the Swamp Island before she murders the hero once she gets her voice back.

Mario and Luigi manage to escape from the Yoshi's Swamp Island, while Yoshi is captured, who babysits and quizzes him on everything he knows about Mario. When her girlfriend visits the Swamp Island once again, playing Tea party with a nearby tea set, Rusalka BugMistress practices playing at the same time, Yoshi giving her pointers. Later, when Six Heroes members try to rescue Yoshi, they run into Rusalka BugMistress, who wanted to talk with Mario, and they escape, but not with Yoshi until they had a fight battle against her to remove the Satan's Curse.

After Six Heroes finally defeats Rusalka BugMistress, she's become Bianca Beakley but her voice continues being horribly, Mario has to agree to give the Esuna Voice Pill to Bianca in exchange for Envy Key, much to later's delight.

After healing her throat with a Health water bottle, she hugs Red plumber and thanks him warmly before giving him the Envy Key before bidding him and Yoshi a fond farewell to accept the friendship. It was after Bianca Beakley (Bugmaster) redeemed herself for getting her throat to recover. As Mario and Yoshi were about to sneak back into the Odyssey Airship, Yoshi watched Bianca from a distance as she called for Cinnamon Teal's attention by listening to the real voice. However... Cinnamon Teal notices Bianca Beakley and meets her up, but callously dismisses her as uninteresting and dumps her aside in a box. After being dumped, she revealed that her girlfriend is Aynaet Teal.

A discouraged and heartbroken Bianca offers Rosalina to give her voice box back as she "doesn't need it anymore" and wants her evil voice back, but Rosalina refuses and insists she keep it. She tells Six Heroes to stay away from her at first, but eventually joins the gang after being offered a chance to defeat Aynaet Teal and be loved by her girlfriend Cinnamon Teal. They are helping her to find her girlfriend on another Island before Bowser, King K. Rool, and King Dedede confront them for what happens until going to find Aynaet Teal for helping wanted.

Despite the event over Yoshi's Swamp Island's conclusion, Bianca Beakley is used to helping the Six Heroes to find her girlfriend by getting rid of the Satan's Curse until she's dating her back for making out before giving the Lust Key and frees the Mario's Friends when Aynaet Teal is gone.

The Rusalka BugMistress from Mario: I Wanna be The Insane 4 (C) me
Bianca Beakley/Bugmaster from Darkwing Duck (C) Disney